Reproduction of images from printed surfaces



May 26, 1970 w. P. TAYLOR 3,514,306

REPRODUCTION OF IMAGES FROM PRINTED SURFACES Filed Aug. 4, 1966 m l z/vm? M I? 7 United States Patent 3,514,306 REPRODUCTION OF IMAGES FROM PRINTED SURFACES William P. Taylor, Hamilton, Ohio, assignor to U.S. Plywood-Champion Papers Inc., a corporation of New York Filed Aug. 4, 1966, Ser. No. 570,294 Int. Cl. B41m 5/00 U.S. Cl. 117--1.7 9 Claims ABSTRACT OF THE DISCLOSURE The reproduction of images from printed surfaces, such as printed paper, by placing a moistened copy sheet against the printed surface to reproduce the image on the copy sheet. The reproduction of images can be effected in the absence of special heat and light and in a matter of seconds. Water moisture alone is suitable for use in moistening the copy sheet and the copy sheet can be packaged for use by merely removing it from its package and placing it in contact with a printed document to reproduce the printed image in the copy sheet in a permanent form.

This invention relates to the reproduction of images, or more particularly, to the making of copies from a printed surface by placing a copy sheet against the printed surface to effect the reproduction of the image on the copy sheet.

The reproduction of images in accordance with the present invention relates to the new concept in copying, described in my copending application Ser. No. 498,821 filed Oct. 20, 1965 in which an image on a printed sheet may be reproduced on a copy sheet simply by holding the copy sheet on the printed sheet for a few seconds without any special application of electricity, heat, or the like. The present invention extends the discovery described in that application, namely, that when the moisture contents of the printed and copy sheets are different, moisture vapor will migrate from one sheet to the other to a greater extent in the non-image areas than in the image areas. This selective vapor migration is due, in part, to the fact that printing ink or the physical change in the structure of the sheet produced by the printing process which establishes the image areas provides a barrier to the migration of vapor at the image areas.

The present invention is based on the discovery that a permanent discernible image of a printed sheet can be produced on a copy sheet whose surface is moistened by a substance capable of permanently altering the optical properties of that surface simply by holding the moistened surface against the printed sheet for a short period of time.

In copending application Ser. No. 498,821, under the selective dissolution embodiment, a multi-component system for moistening the copy sheet film was described. One of the components was a solvent and the other component was an inert liquid carrier for the solvent. There it was suggested that the printed sheet had a disparate avidity for the carrier liquid so that when the copy sheet was placed in contact with the printed sheet, the carrier liquid would be sorbed in the printed sheet to a greater extent than the solvent, in those areas overlying the nonimage portion of the printed sheet, and as a consequence the solvent would act upon the film to transparentize it.

It has now been found that the multi-component moistening substance is not necessary in every case to produce images. Rather, images can be produced where the moistening substance is a single liquid which is capable "ice of changing the optical properties of the film and the liquid can be water.

In accordance with the present invention, a base sheet which is relatively impermeable to moisture as compared to the printed sheet has a thin film formed on its surface. The thin film is capable of retaining moisture of a sensitizing liquid and is capable of having its optical properties changed by that moisture.

The film is moistened and while moist, is held against the printed sheet whose image is to be reproduced. The printing on the sheet provides a condition whereby the printed sheet has a disparate sorptivity for moisture as between the image and non-image area. When the moistened film is held against the printed sheet for a short period of time and removed, an image is produced in the film.

The precise mechanism through which the physical characteristic of the film is changed to produce the image is not completely understood. Rather than present any theory as to the production of images, certain empirically obtained conditions will be set forth.

THE BASE SHEET The base sheet should be relatively impermeable to the sensitizing moisture for otherwise the moisture would tend to migrate into the base sheet rather than remaining in the film. The base sheet should also be transparent in the preferred form of the invention for the image which is produced is a mirror image of the printed sheet and can be most conveniently viewed through the reverse side of the base sheet. Suitable materials for the base sheet include glass, polyethylene, cellulose acetate, Saran, polystyrene, polypropylene, and the like.

THE FILM The film is a substance which is capable of retaining the moisture of the sensitizing liquid and is capable of having its optical properties changed by that moisture. In the examples which are set forth below, it appears that the change in optical properties is due to a change in the light scattering properties of the film. Over certain areas, the imaged film is discontinuous and those areas are relatively opaque. Over the remaining areas, the film is relatively transparent. The transparentizing of the film has probably been caused by the change of the discontinuities in the film as by the surface tension forces on the film.

The film is preferably very thin, that is, in the range of 0.25 to 15 microns and preferably in the range of 510 microns. As to the lower limit, the film must be thick enough to contain light scattering discontinuities and the optimum size of such discontinuities is approximately micron. Further, since it is impossible as a practical matter to deposit a coating which is of an absolutely uniform thickness, the coating deposited should have an average thickness great enough to provide assurance that there are no significant areas which are below the absolute minimum thickness. There is no technically precise upper limit on the thickness of the film but important practical considerations are involved. It is desired to keep the film thin in order to avoid transferring any more than a necessary amount of the vapor of the sensitizing liquid. Further, to change the optical properties of the film, it is necessary that the optical properties be changed comletely through the thickness of the film so that the changes can be perceived. The thicker the film, therefore, the longer is the time required for the imaging process to go to completion. It is preferable that this length of time be of the order of ten seconds for this is short enough for convenience and ease of determination.

Suitable films are organic polymers including vinyl polymers, polycarboxylates, and cellulosic compounds. Specific examples are a copolymer of polyvinyl acetatecrotonic acid, a mixture of ethylene-maleic anhydride copolymer and polyvinyl acetate, cellulose nitrate, and celluose acetate butyrate.

THE SENSITIZING LIQUID The sensitizing liquid preferably is water. Water not only produces the desired result of changing the optical properties of the selected film but additionally is colorless, odorless, and non-toxic and has no adverse effect on the printed pages to which it is exposed. Water can, of course, be mixed with other materials such as those disclosed in the copending application in the selective dissolution process or materials which will affect surface tension or evaporation rate. The sensitizing liquid can also be a non-aqueous volatile compound such as oxygen containing organic compounds including Z-ethyl hexanol, propylene glycol, and hexylene glycol. There are even indications that subliming substances can be effective as sensitizing media.

The amount of sensitizing liquid applied to the film should be just sufficient to moisten the film thoroughly and without any excess moisture in the form of droplets on the surface of the film. For example, the amount of moisture would be that remaining after a film had been wet and subsequently blotted to remove all free standing water.

THE PRINTED SHEET The printed sheet is normally formed of cellulose fibers and may or may not be coated with a pigment and binder. The printing on the sheet creates areas of lesser receptivity or permeability to moisture vapor than the unprinted areas. As a consequence, the printed sheet has a disparate sorptivity for the sensitizing moisture as between the image and non-image areas. The term printed sheet here is used to designate not only sheets which have been printed by conventional means as by letterpress, gravure, oifset, and the like but in addition the term is meant to embrace typed, carbon copies, electrostatically reproduced and hand drawn sheets.

REPRODUCING THE IMAGE The reproduction of an image in accordance with the present invention can be aided by reference to the accompanying drawing which is a diagrammatic illustration of the process.

As shown in the drawing, a copy sheet comprises an impermeable base sheet 11 and a film 12. The copy sheet is used to reproduce an image 13 formed in or on the surface 14 of a printed sheet 15. As set forth in copending application Ser. No. 498,821, the process involves the transfer of the vapor of the sensitizing liquid from the film to the printed sheet as contrasted to a liquid diffusion process. In the normal practice of the process, the copy sheet is placed against the printed sheet with the film 12 in contact with the surface of the printed sheet. Under these conditions, the copy sheet contacts the printed sheet only over a very small percent of its area because of the roughness of the printed sheet surface. To demonstrate the fact that the process is one of vapor migration, the process was practiced by separating the copy sheet from the printed sheet by shims indicated at 16, the shims being approximately 0.007 inch thick to space the sheets apart by that amount.

As indicated, the moistened film of the copy sheet is held against the printed sheet for a short period of time as, for example, 2-30 seconds. The length of time should be sufficient to permit the moisture to migrate out of the film to different extents in the respective areas overlying the image and non-image areas of the printed sheet. After the short period of time, the copy sheet is removed from the printed sheet and an image appears in the film of the copy sheet. In some cases the visible image is reproduced while the copy sheet is in contact with the printed sheet. In other cases a latent image will be produced which becomes permanently visible shortly after separation of the copy sheet from the printed sheet.

Depending upon the conditions of the process, the image produced by the process may be a positive as indicated at A or a negative as indicated at B. The term positive means that the image areas indicated at 18 are relatively opaque and the non-image areas indicated at 19 are relatively transparent. The term negative means, referring to B, that the image areas indicated at 20 are transparent and the non-image areas are relatively opaque as indicated at 21.

PRIOR ART There are a number of prior art processes for reproducing images in a film which forms the surface of a copy sheet, these including photographic and thermographic processes. These processes may be characterized generally as requiring (a) the application of external energy such as specially applied light or heat, (b) a chemical reaction in the film which is initiated by the external energy, and (c) more than one step to complete the process. The present process is distinguishable from such prior art processes in that it requires no special externally applied energy. The copy sheet is merely held against the printed sheet for a short period of time to effect the reproduction of an image. No chemical reaction is involved. Rather, the physical structure of the film is selectively altered to effect the change in optical properties. Only one simple step is required, namely, the placing of the copy sheet against the printed sheet for a brief period of time.

EXAMPLE 1 A copy sheet was prepared by coating biaxially oriented polypropylene film with a solution of polyvinyl acetatecrotonic acid adduct containing about 3% crotonic acid in a solvent blend of 180 ml. denatured alcohol, 450' ml. acetone, and 50 ml. water. After the coating was dried, the copy sheet was soaked in water. The film was then blotted free of excess moisture. The moist, coated surface of the copy sheet was then held in uniform contact against a printed sheet for about twenty seconds. After removal of the copy sheet from the printed surface, a permanent mirror image corresponding to the printed matter on the printed sheet was reproduced on the coated side of the copy sheet.

EXAMPLE 2 A sheet of biaxially oriented polypropylene was coated with a solution of one part by weight of ethylene-maleic anhydride copolymer, two parts of polyvinyl acetate resin, and four parts of water in acetone to make parts.

The dried sheet was dipped in Water for five to ten seconds, blotted and wiped free of excess moisture. It was immediately pressed against a printed page for five seconds and exposed to air until it developed a readable positive image, which took about twenty seconds. Another piece of the coated film, similarly moistened and wiped, was exposed to air for ten seconds and then held in contact with a printed document for twenty to thirty seconds. A permanent negative image resulted.

EXAMPLE 3 A sheet of polystyrene was coated with an 8% solution of cellulose nitrate in a solvent blend of methanol-acetone (4-1 volume ratio) and then dried. The coated sheet was then dipped in a 5% ethylene carbonate aqueous solution for about 10 seconds, and then blotted for about 20 seconds with an absorbent paper towel. The moist, coated surface was then placed in uniform contact with a glass plate, a portion of which was covered with a piece of paper. After thirty seconds of uniform contact with the glass and mounted paper, the coated polystyrene sheet was removed and upon exposure to air, the area of the coated sheet overlying the impervious glass was more opaque than the area overlying the paper.

EXAMPLE 4 A polystyrene sheet was coated with cellulose nitrate as in Example 3. The coated sheet was then dipped in butyrolactone aqueous solution, blotted with a paper towel and then held in uniform contact with an aluminum sheet, a portion of which was covered with a piece of paper. After about seconds, the coated polystyrene sheet was removed and exposed to air. The area overlying the impervious aluminum surface was more opaque than the area exposed to the paper.

EXAMPLE 5 A coated polystyrene sheet was prepared as in Example 3. The coated polystyrene sheet was then dipped in a 5% ethyl carbonate aqueous solution for about 10 seconds, blotted and then exposed for about 30 seconds to the aluminum and paper surface as in Example 4. Upon removal and exposure to air, the area of the coated sheet overlying the impervious aluminum surface was more opaque than the area overlying the paper.

EXAMPLE 6 A sheet of polystyrene was coated with a 2% solution of a carboxylated polyvinyl acetate (Vicol 1260 by Colloids Incorporated). The solution was prepared by blending 3 grams of the copolymer, 10 ml. ethyl acetate, 10 ml. water and enough methanol to make 150 ml. of solution. After the coating dried, it was white and transluscent. The coated sheet was then wiped with 2-ethyl hexanol, and excess liquid was removed by blotting. The coated sheet was placed in uniform contact with a printed page of paper for about one-half hour. The sheet and printed paper were parted and a readable negative image of the printing was visible on the coated polystyrene.

EXAMPLE 7 Example 6 was repeated except that an aluminum window screen was positioned between the printed paper and the coated polystyrene sheet. After about one hour and ten minutes, the coated sheet was removed and a. visible image of the printing and of the screen was reproduced thereon.

EXAMPLE 8 A polystyrene film was coated with a solution of a vinyl acetate-crotonic acid copolymer as in Example 1. The film was then wiped on its coated side with propylene glycol, then blotted free of excess liquid and exposed to a printed paper document for about one-half hour. Upon removal of the polystyrene film, a visible image reproduction of the printed matter was discernible when the film was viewed at an angle.

EXAMPLE 9 The procedure of Example 8 was repeated except that two metal strips, 0.007 inch thick, were positioned about one inch apart between the printed paper document and the treated film. The printed paper was prevented from contacting the surface of the coated polystyrene film by maintaining the paper in a fiat plane away from the film surface. After about two hours, the film was removed and when viewed at an angle, an image reproduction of the printed matter was visible.

EXAMPLE 10 A sheet of polystyrene was coated with a cellulose nitrate blushing lacquer as in Example 3 and dried. The sheet was then dipped in hexylene glycol and the excess liquid blotted off. The coated film was then placed for about seven hours in uniform contact with an aluminum sheeting, a portion of which Was covered by paper. At the end of this time, the area of the coated sheet exposed to the aluminum was more transparent than the area exposed to the paper.

6 EXAMPLE 11 A sheet of polystyrene was coated with a blushing lacquer of cellulose acetate butyrate and dried to an opaque condition. The sheet was dipped in a solution of ten parts by volume of glycol acetate in ninety parts by volume of water until it showed a visible uniform drop in opacity, indicating saturation (about 10-30 seconds), the excess liquid was wiped off and the moist film was held in contact with a printed page for about fifteen seconds. A readable positive resulted. Similar, even improved, results were obtained using a 7 /2 percent solution of glycol diacetate in water.

EXAMPLE 12 The steps of Example 11 were repeated using a film coated with a blushing lacquer of cellulose acetate and a readable positive resulted.

EXAMPLE 13 The steps of Example 11 were repeated using a film coated with a blushing lacquer of cellulose nitrate which was held in contact with printing from 5-10 seconds. A readable positive resulted.

EXAMPLE 14 A sheet of polystyrene was coated with a solution of 4.5 g. polyvinyl acetate in 75 ml. acetone, 75 ml. methanol, 10 ml. glycerine, 10 ml. dioxane and 5.5 ml. water and dried. The film was soaked in water and, after wiping off the excess water to leave a moist film, the film was exposed to a printed page for a few seconds and faint but recognizable images resulted.

EXAMPLE 15 A sheet of polypropylene was coated with a solution constituted by 6 grams of polyvinyl acetate-crotonic acid adduct containing about 3% crotonic acid, 0.75 gram of a carboxy polymethylene resin (Carbopol 934 by B. F. Goodrich) dissolved in 1.0 ml. diethylene glycol, 30 ml. methanol and acetone to make 200 ml. The coating was dried and subsequently moistened with water. The moist coated surface was held in contact with a printed sheet about 20 seconds, producing a recognizable positive. The image was actually formed by an increase in the opacity of the areas overlying the images on the printed sheet, the non-image areas remaining hazy or translucent.

What is claimed is:

1. In the process of making copies from a printed sheet, which comprises the steps of forming on an impermeable base sheet a very thin opaque porous solid film of a substance which will retain the moisture of a sensitizing liquid and Whose optical properties can be permanently altered by diffusion of said sensitizing liquid, moistening said film with said sensitizing liquid, holding said base sheet with said moistened film against said printed sheet for a time sufficient for the moisture of said sensitizing liquid to diffuse from said film toward said printed sheet to a greater extent in the unprinted areas of said printed sheet, and thereafter removing said base sheet from said printed sheet, whereby a permanent mirror image is reproduced in said film due to a change in the optical properties by transparentizing or opacifying said film,

the improvement which comprises, employing a sensitizing liquid consisting of a single liquid selected from the group consisting of water and a non-aqueous volatile organic compound.

2. The method of claim 1 wherein said impermeable base sheet is transparent so that the image formed is right reading when viewed from the transparent base side.

3. The method of claim 1 wherein the printed sheet is printed cellulosic paper and the single liquid is water.

4. The method of claim 3 wherein the thickness of said opaque solid film is approximately in the range of 0.25 to 15 microns.

5. The method of claim 4 wherein the film comprises a hydrophilic substance.

6. The method of claim 5 wherein the hydrophilic substance is an organic polymer from the group consisting of vinyl polymers, polycarboxylates and cellulose compounds.

7. The method of claim 3 wherein said sheet with said moistened film is held against said paper for several seconds.

8. The method of claim 3 wherein said moisture diffuses as a vapor toward said printed sheet.

9. The method of claim 3 which is conducted in the absence of special heat and light.

References Cited UNITED STATES PATENTS 2,503,759 4/1950 Murray 117-37 3,057,999 10/1962 Newman et a1. 250-65 FOREIGN PATENTS 12/ 1965 Belgium. 7/ 1966 France. 11/ 1967 Great Britain.

10 WILLIAM D. MARTIN, Primary Examiner E. I. CABIC, Assistant Examiner US. Cl. X.R. 

